The present invention relates to loading particulate matter into a plurality of moving cavities. In many industrial applications, it is desirable to load relatively fine particulate matter into a series of moving cavities at relatively high speeds. This loading is accomplished by dropping a precisely metered cascade of particulate matter into a preform holding the cavities. The cavities typically are formed between spaced-apart, solid components. While this approach is generally effective, it does suffer from some disadvantages. First, even with a large amount of material in the particulate matter cascade, it is not always possible to fill each cavity completely because the particulate matter does not always settle or compact completely into each cavity. Second, the particulate matter can settle on the solid components rather than fall into a cavity. This spilled material can interfere with the later sealing of the cavity.
The problem described above is particularly applicable to cigarette filter plug manufacture where it is well known to fill the cavities of a continuous filter preform with particulate matter such as carbon granules or some other smoke altering material prior to ultimate use in cigarette filters. These cavities are created between solid cellulose acetate plugs and are wrapped with a porous plug wrap paper. In the prior art, carbon granules deposited in the filter plug preform fill the majority of each cavity. However, it is desirable to maximize this filling as any empty space in a cavity adversely effects air flow in a finished cigarette. Air jets are used to clean the cellulose acetate material by removing any excess carbon granules therefrom. However, this procedure is somewhat unreliable to the extent of missing some of the granules on the cellulose acetate material and also unnecessarily removing some of the granules from the plug cavities.
Accordingly, one of the objects of the present invention is an assembly that enhances particulate matter retention during filling of a moving cavity of a filter plug preform.
Another object of the present invention is a method for enhancing retention of particulate matter in the cavities of a filter plug preform and for removing excess matter from the surface of the preform that includes the step of applying vibration to the preform in the vicinity where the particulate matter is deposited.
In accordance with the present invention, an assembly comprises a transport for continuously moving a filter plug preform in a downstream direction. A particulate matter supply is located in proximity to the transport, and a feed functions to deposit particulate matter from the supply into spaced apart cavities in the moving filter plug preform. A vibrator engages the filter plug preform on the transport to vibrate the preform and thereby enhance particulate matter retention in the cavities.
Preferable the vibrator is an ultrasonic vibrator such as an ultrasonic welder horn. Ultrasonic welder horns vibrate in excess of 20,000 cycles per second. Fundamentally, the vibration is subtle in nature and similar to that of a tuning fork. The present invention utilizes such intense controlled vibration as a cleaning tool, and the vibration is transferred to a filter plug preform as the preform moves along its path of travel during filter plug manufacture.
Particulate matter introduced to the vibrating filter plug preform bounce away from the preform and settle in designated surface cavities in the preform. The vibration functions to enhance particulate matter retention and also to remove a significant amount of any excess particulate matter from the preform.
Preferably, the assembly includes a vacuum source near the transport for removing any particulate matter and recycling that matter to the supply. Moreover, the ultrasonic welder horn may include a horn tip, and the horn tip may have a concave preform engaging surface. Such surface may extend less then 180xc2x0 around the circumference of the perform cavity or more than 180xc2x0, as desired. Alternatively, the horn tip may have a convex preform engaging surface or a flat surface.
The particulate matter may comprise carbon granules loaded into the spaced apart cavities in a filter plug preform.